1. Field
The present disclosure relates to a microstrip transmission line, and more particularly, to a microstrip transmission line having a common defected ground structure and a wireless circuit apparatus having the same.
2. Description of the Related Art
A representative transmission line structure, which is widely used for forming circuits and parts for wireless communication of a radio frequency (RF) and microwave band, is a microstrip transmission line. The microstrip transmission line is manufactured from a printed circuit board (PCB) as illustrated in FIG. 1a and has a planar structure. The structure of the printed circuit board as illustrated in FIG. 1a is well known in the art, and includes metal conductive layers 30 and 50 which are coated at both sides of a dielectric layer 10 with a relative permittivity ∈r and a thickness H, wherein each of the metal conductive layers 30 and 50 has a thickness T.
Referring to FIG. 1b, by removing the metal conductive layer 30 except for a transmission line 40, only the transmission line 40 with a predetermined line impedance Zo and a line width W1 remains on the dielectric layer 10 of FIG. 1a. The widely coated lower metal conductive layer 50 serves as a ground surface.
Although not shown in the drawings, in the structure of the microstrip transmission line, a defected ground structure (DGS) is formed in the ground surface generally through an etching process. The defected ground structure (DGS) is inserted, so that the length of the microstrip transmission line can be reduced, resulting in a reduction of the size of a wireless circuit through the application of the defected ground structure (DGS).
However, although the defected ground structure (DGS) is inserted into the ground surface, since there is a limitation in reducing the length of the microstrip transmission line while maintaining desired electrical performance, it is difficult to improve the degree of integration by minimizing the length of the microstrip transmission line or reducing the size of the wireless circuit without performance deterioration.